NASA/APThe first detailed, all-sky picture of the infant universe. The Wilkinson Microwave Anisotropy Probe (WMAP) image reveals 13 billion+ year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies.

The WMAP has been tracking what’s called “the cosmic microwave background radiation,” or the “afterglow of creation,” which is thought to be the radiation emitted after matter began to cool some 400,000 years after the creation of the universe.

Rachel Kaufman, writing for National Geographic News, explains that the radiation is coming from all directions in the sky. Using precise measurements, researchers can see minor variations in temperature in this radiation—“hot and cold spots that eventually formed the seeds of galaxies.” By matching the spots with other WMAP data and “hundreds of millions of mathematical models of the universe,” Kaufman writes, researchers can figure out which model is the most accurate.

After looking at seven years of WMAP data, scientists determined that the universe is approximately 13.75 billion years old. Previous measurements put the universe at about 13.73 billion years old.

Although 20 million years may not seem like a big deal when you’re talking about billions of years, Kaufman points out that “the new, more tightly defined age will give scientists a better shot at solving some of the great mysteries of the universe, such as dark matter and dark energy.”

Before the WMAP began making such precise measurements, the Hubble Space Telescope had transformed the way astronomers viewed the universe. Launched into orbit on April 24, 1990, the Hubble Telescope orbits the Earth once every 96 minutes, and has now orbited Earth more than 100,000 times since it was put into orbit. Among its many significant discoveries was determining the age of the universe to be about 13 or 14 billion years old, far more accurate than previous measurements that put the universe at anywhere from 10 to 20 billion years old.

The WMAP is a NASA Explorer mission that launched in June 2001 to examine “the properties of our universe as a whole.” Visit the NASA Web site to learn more about WMAP, including its “Top Ten” discoveries.

After the Hubble Telescope determined that the expansion of the universe is accelerating, not slowing down due to gravity, as previously thought, scientists couldn’t explain why. Dark energy and dark matter are part of the solution that theorists came up with to explain the phenomenon. NASA Science explains that dark energy makes up about 70 percent of the universe and dark matter makes up about 25 percent.

“The rest—everything on Earth, everything ever observed with all of our instruments, all normal matter—adds up to less than 5% of the Universe,” according to NASA Science.